Andrews Powder Coating Inc also offers metal plating services. In many cases, it is advantageous to plate the metal prior to powder coating for an extra layer of corrosion barrier, or to provide additional adhesion qualities.
Chem Film is a chemical conversion process that produces a protective chromate surface corrosion resistant film on aluminum and aluminum alloys. Chem Film also acts to passivate the aluminum. Passivation is the chemical neutralization of contaminant iron in the surface of the aluminum or aluminum alloys. Iron is typically transferred by tooling during formation of the aluminum in the mill. The coating can be applied with or without color, the darker coatings providing the greatest corrosion protection. It is usually specified either "clear", meaning with no color, or "gold". There are two types of Chem Film: Hexavalent and the less toxic and RoHS (Restriction of Hazardous Substances) compliant Trivalent formulation.
MIL-C-5541E Type I - Hexavalent Chromium.
Class 1A – Used to provide corrosion protection for painted or unpainted surfaces.
Class 3 – Used to provide corrosion protection on parts requiring low electrical resistance.
These specifications are approved for use by all departments and agencies of the Department of Defense.
TYPE I: No Supplemental treatment.
TYPE II: Supplemental Yellow Chromate treatment. The primary use of chromate finish on Zinc is to retard or prevent formation of white corrion products on Zinc surfaces.
TYPE III: Supplemental Clear Chromate treatment. The primary use of chromate finish on Zinc is to retard or prevent formation of white corrion products on Zinc surfaces.
TYPE IV: Supplemental Phosphate treatment. The primary purpose of phosphate coating on Zinc is to proved a paint base.
Class 1: for decorative application on steel,zinc, copper.
relief is not considered heat treatment).
heating to 500F and above.
Class III: Aluminum alloys nonheat-treatable, and beryllium alloys processed to improve adhesion of the nickel deposit. Coated nonheat-treatable aluminum parts shall be heated for 1 to 1.5 hours at 375°F +/- 15°F to improve adhesion of nickel deposit.
Class IV: Aluminum alloys, heat-treatable, processed to improve adhesion of the nickel deposit. Coated heat-treatable aluminum alloys shall be heated between 240°F to 260°F for 1 to 1.5 hours to improve adhesion of nickel deposit .
Class 1: As-deposited, no heat treatment.
Class 2: Heat treatment at 260 to 400°C (500-752°F) to produce a minimum hardness of 850 HK100.
Class 3: Heat treatment at 180 to 200°C (356-392°F) for 2 to 4-hr to improve coating adhesion on steel and to provide for hydrogen embrittlement relief.
Class 4: Heat treatment at 120 to 130°C (248-266°F) for at least 1-hr to increase adhesion of heat-treatable (age-hardened) aluminum alloys (such as 7075) and carburized steel.
Class 5: Heat treatment at 140 to 150°C (284-302°F) for at least 1-hr to improve coating adhesion for aluminum, non-age-hardened aluminum alloys, copper, copper alloys and beryllium.
Class 2: Thermal treatment at 450°F (232°C) or above to harden the deposit.
Class 3: Thermal treatment at 375°F (191°C) to improve adhesion for nonheat-treatable aluminum alloys and beryllium alloys.